What is the relationship between schizophrenia and substance abuse?

About 50% of people with schizophrenia also have a history of substance abuse or dependence, including alcoholism -a rate three times higher than average. This common combination of problems is sometimes called dual diagnosis. Alcohol, marijuana, and cocaine (in that order) are the substances most commonly involved. Schizophrenic patients who abuse substances are more likely to relapse into psychosis, require hospitalization, neglect antipsychotic medications and other treatments, commit acts of violence, and kill themselves